CakePHP is fundamentally old. It does not avail itself of the capabilities offered in PHP5.3+ and persists in a number of outdated patterns that I consider detrimental to writing good, reusable, maintainable code. It is also incredibly slow, such that it is sort of the "gimme" for people wanting to write benchmarks to show how fast and awesome their new framework is.
Symfony2, on the other hand, is very well-designed (separating entirely from Symfony 1.3 to develop Symfony2 was a great decision), incredibly flexbile, and amazingly performant. It is, no exaggeration, the best PHP system I've ever seen, open-source or otherwise; unless you're Mr. Potencier, reading its code will make you a better PHP programmer. You can actually strip it down so far as to be just a microkernel + dispatch, which is what Silex[1] is. You can also built all manner of whatever-you-want on top of it. There's no real downside to using at least part of the Symfony2 ecosystem for any PHP project.
Symfony2, on the other hand, is very well-designed (separating entirely from Symfony 1.3 to develop Symfony2 was a great decision), incredibly flexbile, and amazingly performant. It is, no exaggeration, the best PHP system I've ever seen, open-source or otherwise; unless you're Mr. Potencier, reading its code will make you a better PHP programmer. You can actually strip it down so far as to be just a microkernel + dispatch, which is what Silex[1] is. You can also built all manner of whatever-you-want on top of it. There's no real downside to using at least part of the Symfony2 ecosystem for any PHP project.
http://silex-project.org/